A woman boils water in a pot for cooking. All of the food consumed during the blood-drinking festival must be brought up to the campsite from the village of Marpha below. The trek uphill takes about four hours.

A woman drinks a glass of fresh yak blood. She is attending the festival with her family in hopes that drinking the blood will help heal her ongoing digestive problems. Some people go for the day; others stay the entire week. The average attendee drinks a glass of blood per day.

"Blood-drinking festival." Reading those words, it's hard not to get either creeped out or curious — especially around Halloween.

I opted for curiosity. Which is how I discovered photojournalist Jana Asenbrennerova's stunning photo essay on an obscure custom that takes place each year in the remote, mist-wrapped highlands of Nepal. These festivals are actually a reflection of the complex relationship that Nepal's Buddhists have with eating meat.

First, to be clear, we're talking yak blood here. Yaks are large, shaggy-haired animals related to cattle that live in the high altitudes of the Himalayas. Up there, yaks graze on herbs that villagers believe are good for digestion but aren't directly digestible by humans.

Yak blood is believed to contain the herbs' medicinal properties and other healthful benefits. "They drink it because they think the blood has healing properties," says Asenbrennerova. And so once or twice a year, villagers undertake an arduous trek up the hillsides to where the yaks roam. They set up camp for about a week, rustle up the yaks, carefully slit their neck veins and cup the blood that pours forth, drinking it while it's still hot.

Then they let the animals go.

"The yaks seem to be fine," says Asenbrennerova. "They don't like it, obviously, but they just run away."

She documented one of these festivals in August of last year in the hills above Marpha, a village in the Mustang District, in the Dhaulagiri Zone of northern Nepal. The festival site was a four-hour hike away, at a spot some 4,000 meters above sea level. What she found was essentially a village camp out.

"They play cards — it's like a big camp for them," she says. "They get to be away from home."

He's attended the festivals in the past — they're "fairly widespread" across the sparsely populated parts of central and western Nepal, he says. Usually around 70 people or so will attend, says Turin, who has spent two decades living in and studying the region. One draw is the social aspect of the events, he says.

But there's another, unspoken motivation: the prospect of yak meat. "A yak is a serious animal," says Turin. "There's a lot of edible meat on a yak."

Let's back up for a second: The staple Nepalese diet consists of rice, lentils and vegetables. Meat is a rarity in the rural parts where the festivals prevail, says Turin. These communities are largely Buddhists, he says — and Buddhists are not allowed to kill animals. They are, however, allowed to eat the meat of an animal who dies by accident. Over-bleeding, he says, is a pretty good "way to accidentally end up with a dead yak."

Asenbrennerova says no animals died during her 24-hour stay at the campsite. But Turin says that's not usually the case.

"Every time I've been to one of these festivals," says Turin, "I've seen one or two yaks accidentally bled to death."